Two-Stage C4 Purification for Polyunsaturated Hydrocarbon Removal
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Solution Overview
Problem
Industrial processes for removing polyunsaturated hydrocarbons from C4 hydrocarbon streams face limitations due to fluctuations in composition and the solubility of hydrogen, which restricts the amount of polyunsaturated hydrocarbons that can be hydrogenated, leading to inefficiencies and side reactions.
Innovation Solution
A two-stage process involving hydrogenation and reaction with mercaptans/disulfides in the first step, followed by selective hydrogenation in the second step using different catalysts and conditions, allowing for increased removal of polyunsaturated hydrocarbons while managing catalyst damage and side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If selective hydrogenation is used to remove polyunsaturated hydrocarbons, then the amount of polyunsaturated hydrocarbons that can be removed is limited by hydrogen solubility, but the process becomes less flexible to composition fluctuations
Solution Approach 1:
The patent divides the polyunsaturated hydrocarbon removal process into two sequential stages: first extractive distillation to reduce polyunsaturated content to ≤1% by weight, then selective hydrogenation for near-complete removal. This segmentation allows each stage to operate within optimal parameters, with the first stage handling bulk removal不受 hydrogen solubility limits, and the second stage achieving high purity conversion.
Solution Approach 2:
The extractive distillation step is performed as a preliminary action before selective hydrogenation. This preliminary removal of the majority of polyunsaturated hydrocarbons (particularly 1,3-butadiene) reduces the burden on the subsequent hydrogenation stage, allowing it to operate with smaller hydrogen requirements that remain within solubility limits while maintaining flexibility to composition variations.
2Productivity
If the maximum amount of hydrogen that can be dissolved is used, then more polyunsaturated hydrocarbons can be hydrogenated, but the process cannot handle composition fluctuations
Solution Approach 1:
The patent employs dynamic control of hydrogen addition rates and process conditions in the selective hydrogenation stage. By adjusting hydrogen flow rates, temperature, and pressure based on real-time composition monitoring, the process maintains high conversion efficiency while adapting to natural composition fluctuations in the C4 hydrocarbon feedstock.
3Quantity of substance
If extractive distillation is used to reduce polyunsaturated content, then the polyunsaturated content is reduced to ≤1% by weight, but further complete removal requires additional steps
Solution Approach 1:
The patent combines extractive distillation and selective hydrogenation into an integrated two-stage process where the output of the first stage directly feeds the second stage. This merging eliminates intermediate storage and handling steps, optimizes material flow, and achieves near-complete polyunsaturated hydrocarbon removal through the complementary actions of both units.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process enables the removal of almost twice the permitted amount of polyunsaturated hydrocarbons, absorbing composition fluctuations and minimizing side reactions, resulting in a more flexible and efficient purification of C4 hydrocarbon streams.
Implementation Method 1
selective hydrogenation of the polyunsaturated hydrocarbons still present in the presence of hydrogen
Implementation Method 2
a selective hydrogenation of the polyunsaturated hydrocarbons still present in the presence of hydrogen
Data Source
AI summary
The present invention provides a two-stage process for removing polyunsaturated hydrocarbons from C4 hydrocarbon streams that, in addition to C4 hydrocarbons, also contain C5 hydrocarbons and mercaptans and/or disulfides.